Numerical modelling of concrete curing, regarding hydration and temperature phenomena

A numerical model that accounts for the hydration and aging phenomena during the early ages of concrete curing is presented in a format suitable for a finite element implementation. Assuming the percolation of water through the hydrates already formed as the dominant mechanism of cement hydration, the model adopts an internal variable called hydration degree, whose evolution law is easily calibrated and allows an accurate prediction of the hydration heat production. Compressive strength evolution is related to the aging degree, a concept that accounts for the influences of the hydration and curing temperature on the final mechanical properties of concrete. The model capabilities are illustrated by means of a wide set of experimental tests involving ordinary and high performance concretes, and through the simulation of the concrete curing on a viaduct deck of the Öresund Link

Nonlinear Modes of Vibration and Internal Resonances in Nonlocal Beams

A nonlocal Bernoulli-Euler p-version finite-element (p-FE) is developed to investigate nonlinear modes of vibration and to analyze internal resonances of beams with dimensions of a few nanometers. The time domain equations of motion are transformed to the frequency domain via the harmonic balance method (HBM), and then, the equations of motion are solved by an arc-length continuation method. After comparisons with published data on beams with rectangular cross section and on carbon nanotubes (CNTs), the study focuses on the nonlinear modes of vibration of CNTs. It is verified that the p-FE proposed, which keeps the advantageous flexibility of the FEM, leads to accurate discretizations with a small number of degrees-of-freedom. The first three nonlinear modes of vibration are studied and it is found that higher order modes are more influenced by nonlocal effects than the first mode. Several harmonics are considered in the harmonic balance procedure, allowing us to discover modal interactions due to internal resonances. It is shown that the nonlocal effects alter the characteristics of the internal resonances. Furthermore, it is demonstrated that, due to the internal resonances, the nonlocal effects are still noticeable at lengths that are longer than what has been previously found

INESC Porto

Good documentation benefits every software development project, especially large ones, but it can be hard, costly, and tiresome to produce when not supported by appropriate tools and methods. The documentation of a software system uses different artifacts, namely source code, for low-level internal documentation, and specific-purpose models and documents, for higher-level external documentation (e.g. requirements documents, use-case specifications, design notebooks, and reference manuals). All these artifacts require continual review and modification throughout the life-cycle to preserve their consistency and value. Good software documents are often heterogeneous, i.e., they combine different kinds of contents (text, code, models, images) gathered from separate software artifacts, a combination usually difficult to maintain as the system evolves over time, considering that source code, models and documents are typically produced and maintained separately in multiple sources using different environments and editors. This paper presents a wiki that helps on quickly weaving different kinds of contents into a single heterogeneous document, whilst preserving its semantic consistency. The fundamental goal of this wiki (XSDoc Wiki) is to reduce the development–documentation gap by making documentation more convenient and attractive to developers. An example taken from the JUnit framework documentation helps to illustrate the features more relevant to do such weaving

LOME – Laboratório de Óptica e Mecânica Experimental

This paper presents a methodology to do morphing between image represented objects, attending to their physical properties. It can be used amongst images of different objects, or otherwise, between different images of the same object. According to the used methodology the given objects are modelled by the Finite Element Method, and some nodes are matched by Modal Analysis. Then, by solving the Dynamic Equilibrium Equation the displacement field is determined, which allows the simulation of the objects ’ deformation. This physical approach also allows the computation of the involved strain energy, therefore the estimated morphing can be represented by the local or global strain energy values. This paper also describes the solution used to simulate only the non-rigid components of the involved deformation

Direct Driven Axial Flux Permanent Magnet Generator for Small-Scale Wind Power Applications

Abstract. Small-scale wind power applications require a cost effective and mechanically simple generator in order to be a reliable energy source. The use of direct driven generators, instead of geared machines, reduces the number of drive components, which offers the opportunity to reduce costs and increases system reliability and efficiency. For such applications, characterized by low speed of rotation, the axial flux permanent magnet generator is particularly suited, since it can be designed with a large pole number and high torque density. This paper presents an axial flux permanent magnet synchronous generator, double sided with internal rotor and slotted stators. Such a structure gives a good compromise between performance characteristics and feasibility of construction. The design process of the machine is described and validated by test experiments